Among conventional liquid bags comprising a bag main body constructed of a flexible thermoplastic resin sheet, known are liquid bags 1, 2 and 3 mentioned below.    1. A liquid bag wherein a mouth member having one mouth portion is sealingly bonded to a part of the periphery of a bag main body shaped like an envelop.    2. A liquid bag wherein a mouth member having two mouth portions is sealingly bonded to a part of the periphery of a bag main body shaped like an envelop (For example, Japanese Unexamined Patent Publication No. 2000-190997).    3. A double-chamber liquid bag wherein a mouth member having one mouth portion is sealingly bonded to a part of the periphery of a bag main body shaped like an envelop and wherein parts of opposed sheets of the bag main body are heat-welded by a special heat-sealing method to partition an inside of the liquid bag into two chambers. This liquid bag is constructed so that applying a pressure onto one chamber penetrates the welded part partitioning the two chambers and thus liquid preparations contained in each of the chambers are mixed (For example, Japanese Unexamined Patent Publication No. Hei 2(1990)-4671).
Among unsophisticated oxygen inhalers (humidifiers) for supplying oxygen with moisture (water vapor or water in spray form) beforehand added thereto, known is an inhaler wherein an oxygen-introducing pipe is attached to a cylindrical hard bottle. For use of the inhaler, however, sterilized water needs to be introduced therein, which is a cumbersome and time-consuming operation and also poses sanitary problems. For the hard bottle, a disposable hard bottle shaped in a box is also usable. However, such a disposable hard bottle is bulky, which results in an upsize of the production apparatus, increasing the manufacturing costs. The hard bottle is also inconvenient in disposal. For these reasons, it is conceived to add a bubbling function to a liquid bag constructed of a flexible container. However, adding the bubbling function to the liquid bags 1, 2 and 3 makes it necessary to provide another member such as a tube or the like for introducing a gas into the bag main body. Especially for the liquid bags 1 and 3 wherein their ports have only one mouth portion, it is necessary to provide another port having a mouth portion for discharging air introduced in the bag main body to the outside, which results in an increase in the number of parts and the complexity in the manufacturing process, driving up costs.
A main object of the present invention is to provide a liquid bag that makes bubbling possible with a simple structure without increasing the number of parts, a mouth member for the liquid bag and a production method thereof.